1. Field of the Invention
This invention relates to a cassette holder assembly for detachably attaching an ink ribbon cassette thereto, mounted on a carriage or of impact printer.
2. Description of Related Art
An ink ribbon cassette used for an impact printer is held by a cassette holder which is mounted together with a print head on a carriage of the printer and holds an ink ribbon in opposition to a tip side face, or a printing face of the print head. Ink ribbons are generally classified into two types, namely, monochrome ink ribbon, as first ink ribbon, and multicolor ink ribbons, as second ink ribbons, which are respectively composed of a plurality of color ribbons. Cassettes for the ink ribbons are held by cassette holders only for each type. The cassette holder for the monochrome ink ribbon holds the cassette at a position for supplying the ink ribbon to the printing face of the print head. The cassette holder for the multicolor ink ribbon is equipped with a mechanism for shifting the position of the ribbon, and holds the cassette so that a feeding mechanism properly feeds the ribbon of each color to the printing face of the head.
Such a cassette holder is fixedly mounted on the carriage, and replacement of the cassette holder requires a service engineer to work on it, because the replacement involves delicate work. Moreover, users of such a printer usually buy either one of printers for monochrome ink ribbon and for multicolor ink ribbon, or both. Although some cassette holder enables the user to replace it so as to meet with types of the ink ribbon by himself or herself, the cassette holder still raises a problem in laborious replacement of the cassette holder.
In the mechanism for shifting of the ribbon, the back of the cassette is supported so as to be rotatable by the cassette holder, and a cam gear is rotated by a motor incorporated in the cassette holder. A push rod, one end of which is contacted to the cam gear, is moved up and down, so that the cassette contacting the other end of the push rod is swung to feed each color ribbon to the printing face of the print head. Consequently, the shifting mechanism must be provided with a pushrod having a length corresponding to the shift stroke or a thick cam gear, and therefore, the shifting mechanism becomes thick in a vertical direction as a whole, thereby affecting the thickness of the printer.